Nuclear resonance fluorescence experiments with linearly polarized bremsstrahlung were performed to determine parities of strong dipole transitions in 40Ar. A total of 14 transitions—ten of them previously unknown—in the energy range from 4.7 to 10.2 MeV could be identified. From this experiment it is evident that the main dipole strength to bound states is due to E1 excitations. An upper limit of B(M1) [up arrow] <0.5 µN2 was found for individual magnetic dipole excitations in 40Ar in the energy region below neutron threshold.

Pion and proton production are measured to investigate thermal equilibrium in central collisions of 40Ar+KCl at 1.8 GeV/nucleon. The bulk of the pion yield is isotropic in the c.m. system, with an apparent temperature of 58±3 MeV, much lower than the 118±2 MeV of the protons. It is shown that the low pion "temperature" can be explained by the decay kinematics of delta resonances in thermal equilibrium. A (5±1)% component in the pion spectrum is, however, found to have a temperature of 110±10 MeV. The effect on the spectra of possible contributions from collective radial flow is discussed.

The excitation energy of the lowest 1+, T=1 state in 20Ne, which is important for parity nonconservation studies, has been determined in a photon scattering experiment to be 11 262.3 ± 1.9 keV. Values for the gamma -ray branching of this level to the ground state and to the first 2+ level in 20Ne are 84 ± 5% and 16 ± 5%, respectively. NUCLEAR REACTIONS 20Ne( gamma , gamma ), E gamma <18 MeV, bremsstrahlung; measured E gamma , gamma branching. Ne natural targets.

The parities of eleven J=1 levels in 208Pb were determined by nuclear resonance fluorescence scattering of linearly polarized photons. A new 1+ level at Ex=5.846 MeV with Gamma 02 / Gamma =1.2±0.4 eV was found. This level can probably be identified with the theoretically predicted isoscalar 1+ state in 208Pb. All other bound dipole states below 7 MeV with Gamma 02 / Gamma >1.5 eV have negative parity. The 1- assignment to the 4.842-MeV level is of special significance because of previous conflicting results about its parity.